Question

геометрическая прогрессия. b1=625
q=1/5
S5=?

Answer 1

S5=(b1(1-q^n))/(1-q)=(625(1-(1/5)^5))/(1-1/5)=(625(1-1/3125))/4/5=(625*3124/3125)/(4/5)=786